1. Field of the Invention
The present invention relates to a data transmission method and a data transmission system using a packet and, more particularly, to a data transmission system free from the problem of local traffic jams.
2. Description of the Related Art
FIG. 1 shows an example of a conventional arrangement of a data transmission system using a packet. The system shown in FIG. 1 comprises loop transmission line 100, station 102, and terminals 104-1 and 104-2. Transmission line 100 is multiplexed, and station 102 comprises packet controllers 114-1 and 114-2 to which are connected adapters 116-1 and 116-2, respectively. Terminals 104-1 and 104-2, in turn, are respectively connected to adapters 116-1 and 116-2.
The operation of the conventional data transmission system will now be described below.
When the system is in a data transmission mode, data output from terminal 104-1 or 104-2 is supplied to specific packet controller 114-1 or 114-2, through adapter 116-1 or 116-2. The recipient controller then generates a packet, using the input data, and sends the packet out to transceiver controller 112. Controller 112 detects an assigned band specific to the controller which has sent out the packet, multiplexes the packet in the corresponding band, and transmits it onto transmission line 100.
When the system is in a data reception mode, data on transmission line 100 is received by transceiver controller 112 and sent to one of the packet controllers, in accordance with the band assigned to the received data. When the controller in question detects that the packet it has received from controller 112 is sent to the intrastation, the packet is sent to either terminal 104-1 or 104-2, through adapter 116-1 or 116-2, respectively.
In the above data transmission system, transmission bands or channels are individually assigned to a large number of terminals coupled to a loop transmission line. In this system, even if only one loop transmission line is physically used, it appears as different transmission channels the terminals. Therefore, since the specific channels are assigned to the terminals, respectively, communication between the terminals connected to packet controllers using different channels is not allowed.
Even if a local traffic jam occurs in a specific packet controller in the station, this cannot be eliminated (the load cannot be redistributed). In addition, the processing speed of the packet controller must be matched with the transmission speed of the loop transmission line, thus presenting problems in terms of transmission efficiency, transmission speed, and the like.